/*
 * Licensed to Crate under one or more contributor license agreements.
 * See the NOTICE file distributed with this work for additional
 * information regarding copyright ownership.  Crate licenses this file
 * to you under the Apache License, Version 2.0 (the "License"); you may
 * not use this file except in compliance with the License.  You may
 * obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
 * implied.  See the License for the specific language governing
 * permissions and limitations under the License.
 *
 * However, if you have executed another commercial license agreement
 * with Crate these terms will supersede the license and you may use the
 * software solely pursuant to the terms of the relevant commercial
 * agreement.
 */

package io.crate.expression.scalar.conditional;

import io.crate.data.Input;
import io.crate.metadata.NodeContext;
import io.crate.metadata.Scalar;
import io.crate.metadata.TransactionContext;
import io.crate.metadata.functions.Signature;

import java.util.Comparator;

abstract class ConditionalCompareFunction extends Scalar<Object, Object> implements Comparator<Object> {

    private final Signature signature;
    private final Signature boundSignature;

    ConditionalCompareFunction(Signature signature, Signature boundSignature) {
        this.signature = signature;
        this.boundSignature = boundSignature;
    }

    @Override
    public Signature signature() {
        return signature;
    }

    @Override
    public Signature boundSignature() {
        return boundSignature;
    }

    @Override
    public Object evaluate(TransactionContext txnCtx, NodeContext nodeCtx, Input<Object>[] args) {
        assert args != null : "args must not be null";
        assert args.length > 0 : "number of args must be > 1";

        if (args.length == 1) {
            return args[0].value();
        }

        Object result = null;
        for (Input<?> input : args) {
            result = extrema(result, input.value());
        }

        return result;
    }

    private Object extrema(Object value1, Object value2) {
        if (value1 == null) {
            return value2;
        } else if (value2 == null) {
            return value1;
        }
        return compare(value1, value2) < 0 ? value1 : value2;
    }
}
